This application is based on and incorporates herein by reference Japanese Patent Application No. 2000-224045 filed on Jul. 25, 2000 and Japanese Patent Application No. 2000-228842 filed on Jul. 28, 2000.
1. Field of the Invention
The present invention relates to a motor having a clutch.
2. Description of Related Art
FIGS. 9 to 11 show one previously proposed motor used, for example, in a power window system. As shown in FIG. 9, the motor includes an oblate motor main body 82, an oblate output unit 84 and a clutch 85 (FIGS. 10 and 11). The motor main body 82 includes a rotatable shaft 81. The output unit 84 includes a worm shaft 83. The clutch 85 transmits rotation of the rotatable shaft 81 to the worm shaft 83 but prevents transmission of rotation of the worm shaft 83 to the rotatable shaft 81.
As shown in FIG. 10, the clutch 85 includes a driving-side rotator 86, a driven-side rotator 87, a collar 89 and rolling elements 90. The driving-side rotator 86 is secured to a distal end of the rotatable shaft 81. The driven-side rotator 87 is secured to a base end of the worm shaft 83. The collar 89 is secured to a gear housing 88 of the output unit 84 to surround both the driving-side rotator 86 and the driven-side rotator 87. The rolling elements 90 are arranged between the driven-side rotator 87 and the collar 89.
An annular recess 86a having diametrically opposing flat inner surfaces is formed in the axial center of the driving-side rotator 86. An annular protrusion 81a having diametrically opposing flat outer surfaces formed in the distal end of the rotatable shaft 81 is fitted within the annular recess 86a, so that the rotatable shaft 81 is connected to the driving-side rotator 86 to rotate integrally with the driving-side rotor 86.
On a worm shaft 83 side of the driving-side rotator 86, protrusions 86b are arranged at predetermined angular positions at radially outward region of the driving-side rotator 86. Each protrusion 86b extends outwardly in a radial direction and also extends toward the worm shaft 83 side in an axial direction. A plurality of recesses 87a are formed at predetermined angular positions at a radially outward region of the driven-side rotator 87. A radially inward portion (where a rubber component G is arranged) of each protrusion 86b is received within the corresponding recess 87a of the driven-side rotator 87 in such a manner that a predetermined circumferential space is provided between each protrusion 86b and the corresponding recess 87a. Control surfaces 87b are provided in radially outer surfaces of protruded portions of the driven-side rotator 87 that are formed between the recesses 87a. A radial space between an inner peripheral surface of a cylindrical portion 89a of the collar 89 and each control surface 87b varies in a circumferential direction. Each rolling element 90 is arranged between the corresponding control surface 87b and the cylindrical portion 89a. 
An annular disk portion 89b that extends radially inwardly is formed at one end (upper end in FIG. 10) of the cylindrical portion 89a of the collar 89. An annular cover plate 91 is fitted within the other end (lower end in FIG. 10) of the cylindrical portion 89a. The cover plate 91 and the annular disk portion 89b limit axial movement of the driving-side rotator 86, the driven-side rotator 87 and the rolling elements 90. That is, in order to hold the protrusions 86b of the driving-side rotator 86 and the rolling elements 90 within the collar 89, an inner diameter of a central opening of the disk portion 89b is selected in such a manner that the disk portion 89b prevents the protrusions 86b and the rolling elements 90 to pass through the central opening of the disk portion 89b. The other end of the cylindrical portion 89a (lower end in FIG. 10) is securely fitted within a serrated annular groove 88a formed in the gear housing 88.
In the motor having the above structure, the driven-side rotator 87, to which the driving-side rotator 86, the rolling elements 90 and the worm shaft 83 are mounted, is received within the collar 89. Then, the cover plate 91 is fitted within the collar 89 to hold the driving-side rotator 86, the rolling elements 90 and the driven-side rotator 87 within the collar 89. Next, the worm shaft 83 is received within a worm-shaft receiving recess 88b of the gear housing 88.
Thereafter, a yoke 92 of the motor main body 82 is connected to the gear housing 88 of the output unit 84, and the protrusion 81a is fitted within the recess 86a to secure the rotatable shaft 81 to the driving-side rotator 86.
In the clutch 85, when the motor main body 82 is driven to rotate the rotatable shaft 81 and thereby the driving-side rotator 86, each rolling element 90 is pushed by a radially outward portion of the corresponding protrusion 86b, and a wall surface of each recess 87a of the driven-side rotator 87 is pushed by a radially inward portion of the corresponding protrusion 86b. As a result, the driving-side rotator 87 and the worm shaft 83 are rotated together.
On the other hand, in a non-actuated state of the motor main body 82, if the driven-side rotator 87 is forcefully rotated along with the worm shaft 83, each rolling element 90 is soon clamped between the corresponding control surface 87b and the inner peripheral surface of the collar 89 to prevent further rotation of the driven-side rotator 87 (locked state), as shown in FIG. 11.
When each rolling element 90 is clamped between the corresponding control surface 87b and the inner peripheral surface of the collar 89 (locked state), a pressure is applied to the circumferential end of the corresponding control surface 87b from the rolling element 90 in a generally radially inward direction (direction of arrow B in FIG. 11). When rapid rotation of the driven-side rotator 87 is abruptly locked, the circumferential end of the engaging projection 87c where the rolling element is located can be deformed or damaged. Furthermore, after the driven-side rotator 87 is locked multiple times, the circumferential end of the engaging projection 87c can be also deformed or damaged, disadvantageously decreasing durability of the clutch.
During assembly of the above-described motor, each component 86, 87, 90, 91 of the clutch 85 is first installed on the collar 89. Then, the assembled clutch 85 is installed in the gear housing 88. Thus, the base component, on which the other components are installed, is switched from one component (collar 89) to the other component (gear housing 88), resulting in a change in an installing direction of the components. This causes a tedious and time consuming assembling work.
To avoid this, it is desirable to sequentially assemble each component of the clutch 85 on the gear housing 88 that acts as the base component. However, once the driven-side rotator 87, the rolling elements 90 and the collar 89 are installed in the gear housing 88, the driving-side rotator 86 cannot be installed within the collar 89. This is due to the fact that the disk portion 89b of the collar 89 prevents the installation of the driving-side rotator 86 within the collar 89.
The present invention addresses the above disadvantages. Thus, it is an objective of the present invention to provide a motor provided with a clutch having a structure that allows sequential assembly of the clutch on a gear housing of the motor and is capable of retaining each rolling element within a collar of the clutch upon completion of the assembly. It is another objective of the present invention to provide a motor having a clutch that can restrain deformation or damage of a driven-side rotator thereof.
To achieve the objectives of the present invention, there is provided a motor having an oblate motor main body, an output unit and a clutch. The motor main body has a rotatable shaft. The output unit has a housing and a worm shaft. The housing is secured to the motor main body. The worm shaft is supported within the housing. The clutch is arranged between the rotatable shaft and the worm shaft. The clutch transmits rotation of the rotatable shaft to the worm shaft and prevents transmission of rotation of the worm shaft to the rotatable shaft. The clutch includes a driving-side rotator, a generally cylindrical collar, a driven-side rotator, at least one rolling element, a support member and a stopper. The driving-side rotator is arranged to rotate integrally with the rotatable shaft. The collar is secured to the housing. The driven-side rotator is arranged to rotate integrally with the worm shaft. The driven-side rotator is located within the collar in a coaxial manner with respect to the driving-side rotator and has at least one control surface. Each of the at least one control surface is spaced from the collar for a distance that varies in a circumferential direction of the collar. The driven-side rotator is drivingly engageable with the driving-side rotator in a rotational direction. Each of the at least one rolling element is arranged between the collar and a corresponding one of the at least one control surface. Each of the at least one rolling element is rotated together with the driven-side rotator when the driving-side rotator is rotated. Each of the at least one rolling element is clamped between the collar and the corresponding one of the at least one control surface to restrain rotation of the driven-side rotator when the driven-side rotator is rotated. The support member rotatably supports the at least one rolling element. The stopper is secured to the housing. The stopper restrains axial movement of the at least one rolling element by restraining axial movement of the support member to retain the at least one rolling element within the collar.
The driving-side rotator may include at least one protrusion. Each of the at least one protrusion is arranged at a predetermined angular position within the collar and extends in an axial direction of the clutch. The driven-side rotator may include a shaft portion, at least one engaging projection and at least one reinforcing rib. The shaft portion is arranged within the collar and is coaxial with the driving-side rotator. Each of the at least one engaging projection is circumferentially engageable with at least one of the at least one protrusion. Each of the at least one engaging projection extending radially outwardly from the shaft portion and has a corresponding one of the at least one control surface at radially outer end surface thereof. The at least one reinforcing rib reinforces the at least one engaging projection.